Effect of subsurface boron on photoluminescence from silicon nanocrystals

Silicon (Si) nanocrystals (NCs) less than 5 nm in diameter are grown on SiO2 surfaces using hot wire chemical vapor deposition in an ultrahigh vacuum chamber and the dangling bonds are passivated using atomic deuterium. The passivated NCs are subsequently exposed to BDx radicals formed by dissociating deuterated diborane (B2D6) over a hot tungsten filament and photoluminescence quenching is observed. Temperature programmed desorption spectra reveal the presence of additional D2 desorption peaks beyond those found for surfaces that have only been passivated by atomic deuterium. The additional peaks appear at lower temperatures and this can be attributed to deuterium desorption from surface Si atoms bonded to subsurface boron atoms. The subsurface boron likely enhances nonradiative Auger recombination leading to photoluminescence quenching.